Partially human mice could help avoid drug trial disasters

PARTIALLY human mice have been created by scientists developing safer forms of drug testing.

The lab mice are injected with human embryonic stem cells, causing them to grow mixed lumps of human tissue.

Once these “teratomas” have formed, researchers can expose them to new drugs.

The technique could help avoid drug trial disasters such as the one which left six British men fighting for their lives two months ago, it is claimed.

The men were hit by an uncontrolled immune reaction after being given an experimental drug designed to treat rheumatoid arthritis, leukaemia and multiple sclerosis. All suffered multiple organ failure.

Scientists were taken by surprise since the drug had earlier been tested on monkeys and found to be safe.

Humanised mice could make such Phase One trials less of a gamble, according to Israeli researchers.

The mice develop growths containing human tissue, including blood vessels, cartilage, fat and connective material.

In tests, they were given a drug that in animals appears effective at treating cancer.

Professor Yoram Reiter of the Technion Institute in Haifa, Israel said: “In ordinary mice, the drug caused the complete disappearance of tumours. But in the mice with human tissue, we saw cells that were resistant to the drug.

“Now we can try to study the cells that don’t respond and use this system to fine-tune the drug.”

The development may help shed light on why “scientists have managed to cure cancer in millions of mice, but not people”, he said.

“We know that humans and mice don’t respond the same way. But you want to know about the differences before you begin human trials. Now you can receive this information at a much earlier stage and improve the design of the drug, without resorting to trial and error on humans.”

Details of the technique appeared yesterday in the journal Cancer Research.

The researchers said human tissue provides a better environment for the growth of tumours than mouse tissue. This often led to overly-optimistic expectations for cancer drugs successfully tested on mice.